The goal of this research is to investigate the effects of sleep restriction and sleep prolongation on cognitive processes in preschool and school-age children as measured by event-related potentials (ERPs). Children throughout the USA frequently face mild sleep restrictions due to a host of pressures - demands of homework, school activities, peer interactions, family activities - that reduce the number of hours of sleep children experience from day-to-day or week-to-week. Such changes can impact the child's ability to attend to classroom studies or other areas that place additional cognitive processing demands on the child. To pursue this goal, 480 children half females, from 4 through 8 years of age will participate in a number of cognitive tasks while their brain electrical activity is recorded. It is anticipated that changes in the topographic recordings of brain electrical patterns across the scalp will change as a function of sleep deprivation and sleep prolongation. Such changes will be characterized by latency shifts that reflect the rapidity in which the brain responds to information. Analyses will also attempt to localize the hypothesized sources within the brain where information is processed. This work will greatly enhance knowledge concerning the role sleep plays in brain and behavior and can lead to the development of a means to identify children potentially at cognitive risk because of chronic sleep restrictions. This is an important first step in minimizing potential negative risks of sleep restriction on cognitive development during the childhood years.